You need to find a 1973 donor Mustang and get the pump, engine pump brackets (3), attaching hardware, steering box, hose retainer bracket(s) and hoses (hoses for length checks). There may also be a fluid cooling radiator which has brackets and one more hose. The same setup may be found on 71-72 Mustangs, 72-73 Torinos and 71-73 Cougars. The brackets and pump are the same on 70-73 full size Fords with a 302 or 351C. My Ford Car Parts book only goes to 1972 so I am assuming that 73 is the same. NPD lists a new pressure hose, 3A719-14A at $25.95, and a rebuilt pump without the reservoir, 3A674-2D for $54.95 plus an $80 core charge. Return hoses are low pressure and called out in bulk.
Jim